Automatic surveillance devices such as, e.g., fire alarms, intrusion detectors, gas detectors and radiation detectors typically are designed for installation at a supporting surface, with a mount component being fastened to the surface and an insert component being fastened detachably to the mount. Included in the insert is a sensor assembly, e.g., for light, heat, gas or hazardous radiation, along with sensor-signal evaluation electronics on a circuit board. An electrical connection is established between the insert and the mount. For protection of the mounted combination, a cover may be installed.
A device of this type in the form of a fire alarm is described in German Patent Document DE-U-9210856.3. The fire alarm has an alarm mount with a connector block, and an alarm insert which includes a sensor assembly, and a printed circuit board with evaluation electronics and with a plug for electrical connection to the connector block. The alarm mount, e.g. consisting of a simple injection-molded part, has a multi-polar connector block with plug sockets, and the alarm insert has a contact pin strip with corresponding contact pins which are engaged with the connector block when the alarm (i.e., the alarm insert together with the alarm cover) is inserted. The alarm insert can be rotated in the circumferential alarm cover, and can be locked in its final position. For this purpose, the alarm insert has a circumferential side wall which functions as a centering ring. The alarm cover can be mechanically interlocked on the alarm mount, in that a locking cam formed on the alarm cover is guided in an obliquely extending gate guide in a locking gate when the alarm is inserted. The gate guide is disposed on the alarm cover such that, to establish contact, there is vertical lifting when the alarm is inserted and twisted in.
There is a risk of damage to the interlocking mechanism due to improper handling of this device. Also, because of the interlocking mechanism with locking gate and locking cam, and because of the way contact is made between the connector block and contact pins in a vertical lifting movement, the device is expensive to make in mass production.
It is especially the way contact is made in a vertical lifting movement which increases the manufacturing costs. This is due to considerable construction costs for bringing the contact pin strip by a first, rotational movement of the alarm into the correct position where it is in alignment with the connector block but still at a distance from the connector block, and then establishing electrical contact gently yet positively in the vertical lifting movement. Also, this type of contacting requires contact pins which are directed vertically upwards from the printed circuit board, making it necessary to mount a separate component on the printed circuit board in a separate manufacturing step.